Patent GB-391298-A (GB)
Title: Improvements in and relating to flash light lamps and the like and to the manufacture thereof
IPC: F21K5/08
Filed: 1932-03-12
Abstract: 391,298. Flashlight lamps. NAAMLOOZE VENNOOTSCHAP PHILIPS' GLOEILAMPENFABRIEKEN, 13D, Emmasingel, Eindhoven, Holland. March 12, 1932, No. 7446. Convention date, May 5, 1931. [Classes 39 (ii) and 75 (i).] A flashlight lamp contains a gas filling from which an actinic effect is obtained by a gas reaction initiated electrically. Suitable gas fillings consist of mixtures of oxygen with carbon mon-oxide, carbon di-sulphide, ammonia, formaldehyde, cyanogen or hydrogen sulphide, and nitrous oxide with hydrogen. The gas filling may alternatively be one which can be decomposed electrically with actinic effect, e.g. chlorazide. In order to avoid danger due to the lamp bursting the gases may be at less than atmospheric pressure. For example carbon mon-oxide and oxygen gas mixture not exceeding 1/3 atmospheric pressure may be employed, a suitable mixture being carbon mon-oxide and oxygen at 10 cm. and 5 cm. mercury pressure respectively. Should air enter to fill the bulb containing such a mixture the proportion of carbon mon-oxide will be less than 16 per cent which forms the lower explosion limit of a carbon mon-oxide and oxygen mixture. Alternatively, the lower explosion limit of the mixture may be raised by the addition of argon, nitrogen, helium, carbon di-oxide, silicon chloride, sulphuryl chloride, or carbon-tetrachloride. To reduce the effects of explosion the lamp bulb may be provided with a gauze envelope coated with transparent varnish or lacquer, or be formed with a double wall. The space between the two walls may be filled with glass wool. Alternatively, the bulb may be protected with a safety fuse or a tube connection with the open air normally sealed by a rubber cap which is removed before ignition is effected. Ignition may be effected by an electrically heated glower filament which may be so chosen that should the bulb become filled with air the temperature of the filament with the normal applied voltage will be below the explosion limit of the mixture, while if extra voltage is applied the filament will melt before the explosion limit is reached. If for example the mixture has a normal explosion temperature of 600‹ C. and an explosion temperature when the bulb is filled with air of 750‹ C. the filament may be of aluminium having a melting point of 660‹ C. Substances, e.g. caustic soda or potash, may be introduced into the bulb to absorb wholly or partially the gas produced by the reaction. In order to improve the actinic effect mercury vapour may be introduced into the gas filling or mercury or mercury compounds may be applied to the filament. The filament may also be coated with salts of sodium, strontium, &c. or neon may be introduced into the bulb for producing coloured light. An ignition mixture composed of 1 part aluminium powder, 10 parts barium peroxide and a small quantity of match igniting material may be applied at various points to the filament to reduce the reaction time. The bulb may be constructed of glass substantially transparent to ultraviolet rays and may be provided on one side with a light-reflecting layer. A manometer or other warning device may be fitted to the bulb to indicate leakage. Lamp bulbs capable of being connected to gas containers for refilling may be employed. Fig. 1 shows a lamp bulb 1 which is exhausted through a tube 5 provided with an aperture 6 covered by a rubber tube 7. After exhaustion the tube 5 is sealed at the point 8, and the tube 7 is displaced to allow the insertion of a tube 10, Fig, 2. through which the gas filling is supplied. The rubber tube may subsequently serve as a safety valve, or the rubber and exhaust tube may be dipped in a fused obturating mass such as picein or sealing wax. In another construction, shown in Fig. 4, the filling tube 12 is drawn slightly away from the exhaust tube 11 after filling has been effected and the stretched portion 14 is pinched. The rubber tube is then cut and the end of the bulb dipped into an obturating mass. The exhaust tube may contain metal gauze to prevent ignition of the gas filling in the bulb while the exhaust tube is being filled. Specification 25369/99, [Class 98, Photography], is referred to. The Specification as open to inspection under Sect. 91 comprises also the use of the method of exhausting and filling the flashlight bulbs in exhausting and filling gas-filled electric incandescent lamps or discharge tubes. This subject-matter does not appear in the Specification as accepted.